<objective Build production-grade multi-agent systems with LangGraph using supervisor, swarm, handoff, router, or master patterns. Enables cost-optimized orchestration with multi-provider routing (Claude, DeepSeek, Gemini - NO OpenAI), guardrails, durable execution, observability, and scalable agent coordination. </objective <quick start State schema (foundation): Pattern selection: | Pattern | When | Agents | |---------|------|--------| | Supervisor | Clear hierarchy | 3-10 | | Swarm | Peer collaboration | 5-15 | | Handoff | Sequential pipeline | 2-5 | | Router | Classify and dispatch | 2-10…